The function and fate of germinal center cells from lymphoid tissue will be analyzed in both mice and chickens. Particular attention will be given to kinetic events and their correlation to functional changes in B memory cells. Localization of radioactively labeled primed and unprimed B cells, and the influence of localized specific antigen on isolated primed B cell localization in recipients, will be followed both morphologically and functionally. Induction of B memory with guinea pig anti-idiotype of the IgG1 isotype will be examined in both normal and thymusless mice. If such priming is obtained, the histological counterpart will be studied. Experiments on receptor blockade of primed B cells will concern the rescue of such cells into responsiveness after exposure to a variety of cellular and chemical influences. Finally, the phenomenon of in vivo recruitment of B cells into proliferation during graft vs. host reactions and the influence on this phenomenon of genetic factors linked to the histocompatibility region will be investigated. The influence of vesicular stomatitis virus on lethal graft vs. host reactions, particularly the possibility of a life-saving effect of the virus by its inhibition of activated T cells, will also be studied.